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Ophthalmology and Visual Sciences

Pellucid marginal degeneration

Pellucid marginal degeneration

Category(ies): Cornea and External Disease
Contributor: Jesse Vislisel, MD
Photographer: Carol Chan, CRA

Pellucid marginal degeneration is a bilateral corneal ectasia that results in inferior corneal thinning with a corneal protrusion above the thinnest area. This is in contrast to keratoconus where maximal thinning occurs at the apex of the protrusion.

slit lamp corenal protrusion OD
Figure 1a: OD These slitlamp photographs demonstrate the corneal protrusion above the area of inferior thinning in a patient with pellucid marginal degeneration.
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slit lamp corenal protrusion OS
Figure 1b: OS These slitlamp photographs demonstrate the corneal protrusion above the area of inferior thinning in a patient with pellucid marginal degeneration.
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Pentacam Scheimpflug cross-sectional image
Figure 2: The Pentacam Scheimpflug cross-sectional images from the patient in Figures 1 show the contour changes associated with the inferior stromal thinning
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Pentacam Scheimpflug cross-sectional image
Figure 3: The axial curvature and anterior float Pentacam topography maps from the patient in Figure 1 reveal the characteristic high against-the-rule astigmatism pattern seen in patients with pellucid marginal degeneration. Inferior steepening is also present, as seen grossly in the images in Figures 1 and 2, but is too peripheral in the case to be captured on the topography scans, thus the absence of the classic "crab claw" topographic appearance.
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Ophthalmic Atlas Images by EyeRounds.org, The University of Iowa are licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

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